New plant pests in horticultural production came as a surprise in 2012

17.1.2013

<p>Plants pests and diseases classified as quarantine pests in the Act on Protecting Plant Health have so far occurred mainly in greenhouse production. However, the year 2012 showed that the spread of new pests to Finland is a real threat also when it comes to outdoor horticultural production.</p>

Two new quarantine diseases were identified in outdoor horticultural production. According to inspections and laboratory analyses, red core disease
(Phytophora fragariae var.
fragariae) was found on 55 strawberry plantations in different parts of Finland. The wet and cool weather of the summer of 2012 favoured the spread of the disease and made it easier to identify the symptoms amongst the plants. As the disease can survive in the soil for at least 15 years without a host plant, it is impossible to eradicate it from contaminated farms. The aim is now to stop the spread of the disease from the contaminated farms to other commercial production.

Apple proliferation disease
(Candidatus Phytoplasma mali) was found in one apple orchard in mainland Finland and in one on Åland. The disease is spread by two species of apple psyllid
(Cacopsylla mali). Apple proliferation phytoplasma cannot be eradicated by chemical means. The spread of the disease will be surveyed both in mainland Finland and on Åland in 2013.

Angular leaf spot
(Xanthomonas fragariae), which was discovered in Finland for the first time in 2011, was observed in one open field strawberry cultivation and in hanging pots production grown under cover. The contaminated plants were destroyed. The monitoring for the symptoms of the disease will continue during the growth period in 2013.

White potato cyst nematode was discovered again

During the course of the surveys, bacterial ring rot
(Clavibacter michiganensis subsp.
sepedonicus) was found in one new cultivation and yellow potato cyst nematode
(Globodera rostochiensis) in 11 new cultivations. The findings of bacterial ring rot and yellow potato cyst nematode were on the same level as in previous years. White potato cyst nematode
(Globodera pallida) was found in two cultivations in Northern Ostrobothnia. The area where the findings were made will be surveyed more in detail during the summer of 2013. Previously, there have been a couple of findings in Finland of white potato cyst nematode in Häme and Satakunta in the early 2000’s.

Colorado beetles
(Leptinotarsa decemlineata) were found in nine potato cultivations. The findings were the descendants of beetles that had drifted to Finland during the summer of 2011. All of the findings were destroyed.

Good situation in greenhouse cultivations and in forestry and timber production

Many quarantine pests and diseases are found in greenhouse production every year. In 2012, the number of findings of pests remained at the normal level, and no new plant diseases or pests were discovered in Finland.

Most of the observations were sweet potato whitefly
(Bemisia tabaci). They were found in a total of 15 cultivations of poinsettia and in one cultivation of bedding plants. Impatiens necrotic spot tospovirus (INSV) was found in two cultivations. There were also isolated findings of chrysanthemum leaf miner
(Liriomyza trifolii) and pea leaf miner
(Liriomyza huidobrensis),Chrysantheumum white rust
(Puccinia horiana) and tomato spotted wilt tospovirus (TSWV). No quarantine pests or diseases were found in vegetable production.

Quarantine pests and diseases usually spread into greenhouse production with cuttings or small plants brought in from abroad. They are almost always destroyed before the plants are sold to consumers.

The pest situation was very good in the forestry and timber sectors, as no quarantine pests or diseases were observed during inspections in 2012.

Plant pests were also found on plants on the market

Quarantine pests and diseases were found in three greenhouse plant batches, in eight batches of plants from nurseries and in three potato batches that were already for sale. A prohibition on marketing was placed on all of the contaminated plant batches.